Implementation of a Sensitive Method to Assess High Virus Retention Performance of Low-Pressure Reverse Osmosis Process.

Human enteric viruses are important etiological agents of waterborne diseases. Environmental waters are usually contaminated with low virus concentration requiring large concentration factors for effective detection by (RT)-qPCR. Low-pressure reverse osmosis is often used to remove water contaminants, but very few studies focused on the effective virus removal of reverse osmosis treatment with feed concentrations as close as possible to environmental concentrations and principally relied on theoretical virus removal. The very low viral concentrations usually reported in the permeates (i.e. at least 5 log of removal rate) mean that very large volumes of water need to be analysed to have sufficient sensitivity and assess the process efficiency. This study evaluates two methods for the concentration of adenoviruses, enteroviruses and MS2 bacteriophages at different viral concentrations in large (< 200 L) and very large (> 200 L) volumes. The first method is composed of two ultrafiltration membranes with low-molecular weight cut-offs while the second method primarily relies on adsorption and elution phases using electropositive-charged filters. The recovery rates were assessed for both methods. For the ultrafiltration-based protocol, recovery rates were similar for each virus studied: 80% on average at high virus concentrations (106-107 viruses L-1) and 50% at low virus concentrations (103-104 viruses L-1). For the electropositive-charged filter-based method, the average recoveries obtained were about 36% for ADV 41, 57% for CV-B5 and 1.6% for MS2. The ultrafiltration-based method was then used to evaluate the performance of a low-pressure reverse osmosis lab-scale pilot plant. The retentions by reverse osmosis were similar for all studied viruses and the validated recovery rates applied to the system confirmed the reliability of the concentration method. This method was effective in concentrating all three viruses over a wide range of viral concentrations. Moreover, the second concentration method using electropositive-charged filters was studied, allowing the filtration of larger volumes of permeate from a semi-industrial low-pressure reverse osmosis pilot plant. This reference method was used because of the inability of the UF method to filter volumes on the order of one cubic metre.

Prospects of industrial membrane concentrates: treatment of landfill leachates by coupling reverse osmosis and wet air oxidation.

Stabilized landfill leachates are characterized by a high chemical oxygen demand and limited biodegradability. This study investigates the removal of the organic fraction (chemical oxygen demand and total organic carbon) using a treatment approach that couples membrane processes and wet air oxidation (operating at 200-300 °C and 18 MPa). The aim is to address the challenges posed by landfill leachate membrane concentrates considering variations throughout the year across three different seasons. The efficiency of the treatment path was assessed through the removal of the chemical oxygen demand and total organic carbon, with additional insights provided by fluorescence spectroscopy to evaluate the degradation of the organic compounds' complexity. The most favorable results were achieved at the highest temperature (300 °C) with removals over 90% for total organic carbon and 87% for chemical oxygen demand, along with a complete elimination of fluorescence. The coupling of membrane processes and wet air oxidation has demonstrated its effectiveness in degrading the organic compounds of landfill leachates. The overall mass balance on the treatment path indicates the feasibility of discharging the treated effluent into the environment, meeting regulatory thresholds for total organic carbon and chemical oxygen concentrations.

Impact of Chlorinated-Assisted Backwash and Air Backwash on Ultrafiltration Fouling Management for Urban Wastewater Tertiary Treatment.

To improve membrane fouling management, the NaClO-assisted backwash has been developed to improve permeability maintenance and reduce the need for intensive chemical cleanings. This study is aimed to focus on the efficiency of NaClO-assisted backwash in real UF pilot scale and with periodic classic backwash (CB) and air backwash (AB). The impacts on hydraulic filtration performance, physicochemical properties of membrane material under different addition frequencies of NaClO, and the performance of chlorinated CB and AB will be discussed. In result, 10 mg Cl2 L-1 NaClO addition in backwash water is confirmed to greatly improve the overall filtration performance and backwash cleaning efficiency. One condition stands out from the other due to better control of irreversible fouling, less NaClO consumption in 10 years prediction, sustainable and adaptable filtration performance, and less potential damage on the physicochemical properties of the membrane. Additionally, it can be inferred from this experiment that frequent contact with NaClO induced some degradation on the PES-made UF membrane surface properties. To retain the best state of UF membrane on anti-fouling and qualified production, the optimized condition with more frequent NaClO contact was not suggested for long-term filtration.

Membrane-Based Processes Used in Municipal Wastewater Treatment for Water Reuse: State-Of-The-Art and Performance Analysis.

Wastewater reuse as a sustainable, reliable and energy recovery concept is a promising approach to alleviate worldwide water scarcity. However, the water reuse market needs to be developed with long-term efforts because only less than 4% of the total wastewater worldwide has been treated for water reuse at present. In addition, the reclaimed water should fulfill the criteria of health safety, appearance, environmental acceptance and economic feasibility based on their local water reuse guidelines. Moreover, municipal wastewater as an alternative water resource for non-potable or potable reuse, has been widely treated by various membrane-based treatment processes for reuse applications. By collecting lab-scale and pilot-scale reuse cases as much as possible, this review aims to provide a comprehensive summary of the membrane-based treatment processes, mainly focused on the hydraulic filtration performance, contaminants removal capacity, reuse purpose, fouling resistance potential, resource recovery and energy consumption. The advances and limitations of different membrane-based processes alone or coupled with other possible processes such as disinfection processes and advanced oxidation processes, are also highlighted. Challenges still facing membrane-based technologies for water reuse applications, including institutional barriers, financial allocation and public perception, are stated as areas in need of further research and development.